But let’s say he is. It does happen. In their landmark 1994 survey of American sex, Edward O. Laumann and colleagues found that having sex made 2.8 percent of married people feel guilty.

Why would a married man feel guilty about sex with his wife? Well, sometimes men can be a little ashamed after the fact. Did you two use porn? Did he make funny wildebeest noises? In the throes of passion did he suggest you have sex with the 1967 Green Bay Packers? Were deli items involved? All that can seem like much more fun before the ejaculation. After, we may wish to hide our shame.

Or maybe he was just raised to think sex was dirty. If so, take that up with his mom.

A: My wife and I have been married for 30 years. I delved in a bi-curious/bisexual phase about five years ago for the oral satisfaction I was not getting at home. My wife discovered this and now considers me to be gay or bi. After her discovery, in an attempt to please me, we entered the swinging lifestyle for about two years. A majority of our encounters were with strictly straight sex, no bi play at all. A few times during our encounters with other men, during the heat of the moment, I performed oral sex on the other man. My wife is totally disgusted with my behavior and our marriage is heading toward divorce. I don’t consider myself gay but I do enjoy the satisfaction I feel giving and receiving oral sex. The bisexual encounters and the swinging encounters were not meant to be combined. I suggested the swinging lifestyle to “spice up” our marriage but my wife thinks I wanted it because of the men. We have not had sex in two years. How common is my situation? Should I even attempt to save this marriage? She states she no longer loves me as a husband.

I know men whose wives won’t let them go to Hooters! And yours finds out about your bisexual experiments and then tries on swinging just to please you? Give that woman a trophy.

According to Eli Coleman, director of the program in human sexuality at the University of Minnesota and one of this nation’s foremost experts in sexual orientations and sexuality, “it is possible for him to be primarily heterosexual with a curiosity about same-sex encounters. That is not so uncommon in the swinging world.”

But he was struck, as I was, by your statement that you dabbled in bisexuality for the oral satisfaction. You do know that women have mouths, too, don’t you? But you picked men. Why?

Coleman explained that you may have picked men because we’re easy. “It is really more about the convenience than it is men being the erotic orientation,” he said. “It is just easier to get oral sex from a man than a woman in this culture. You can go to any rest stop or airport bathroom to prove that.” So maybe you are essentially straight and just went looking for quickie sex.

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Or maybe not. It is equally possible you are hiding. Sometimes, Coleman said, people who say they are “experimenting” or “bi-curious” really are bisexual and don’t want to face it. Or, they could be homosexual “and they just use that term ‘bi-curious’ to justify their ability to explore” being gay. After 30 years of marriage to a woman you just might fear the truth.

Look at this from your wife’s point of view. She made a pretty big effort. Heroic, really. She may feel betrayed. In a small 1989 study of 21 women who had married men expecting straight monogamy, but whose husbands had sex with men, the wives’ “suffering was aggravated by feeling deceived or stupid for not having guessed the truth.”

Back in the 1980s when Coleman studied this phenomenon, he found that marriages could survive situations like yours, but the chances diminished the older the people involved were, the more children they had, the later the man began having homosexual experiences, and if he was getting emotionally involved with any of his male sex partners.

The only way to know what you and your wife should do is to seek therapy, right away, from a therapist trained to address not only marital, but sexual orientation problems (and by “trained,” Coleman means “not just an hour seminar at a conference.” You need an expert.) You can begin by checking the website for the American Association of Sexuality Educators, Counselors and Therapists (www.aasect.org).